As Brandhorst first noted, (H. W. Brandhorst, Jr., Record of 9th Photovoltaic Specialists Conf. (IEEE, New York, 1972), p. 1.) the power conversion efficiency .eta. seen in silicon p-n junction solar cells is considerably less than the maximum theoretical value of .eta. mainly because the open-circuit voltage V.sub.oc is smaller than simple p-n junction theory predicts. Experiments on n.sup.+ -p silicon cells have shown that this discrepancy in V.sub.oc results from the dominance, in the nonilluminated (dark) cell, of the emitter recombination current J.sub.E over the base recombination current J.sub.B. In cells having base doping concentrations of the order of 10.sup.17 cm.sup.-3, for which the largest values of V.sub.oc are seen, J.sub.E exceeds J.sub.B by about an order of magnitude, rather than being several orders of magnitude less than J.sub.B as is predicted by simple p-n junction theory. (F. A. Lindholm, A. Neugroschel, C. T. Sah, M. P. Goodlewski, and H. W. Brandhorst, Jr., IEEE Trans. Electron Devices ED-24, 402 (1977). The excess J.sub.E has been attributed to the mechanisms of energy band-gap narrowing and lifetime degradation that accompany heavy doping concentrations in the n.sup.+ emitter. (F. A. Lindholm and C. T. Sah, IEEE Trans. Electron. Devices ED-24, 299 (1977); C. T. Sah and F. A. Lindholm, IEEE Trans. Electron Devices ED-24, 358 (1977).
To supress J.sub.E and thus raise the achievable value of V.sub.oc, a new structure, the HLE junction solar cell, containing a high-how (H-L) junction in the emitter, has been proposed and its performance has been calculated on theoretical grounds. (C. T. Sah, F. A. Lindholm, and J. G. Fossum, IEEE Trans. Electron Devices ED-25, 66 (1978); J. G. Fossum, F. A. Lindholm, and C. T. Sah, Tech. Digest 1977 Int. Electron Devices Mtg. (IEEE, New York, 1977), U.S. patent application Ser. No. 966,360, filed Dec. 4, 1978, Lindholm, Fossum and Sah.)